We present results of the reduction of the archive
spectra of the nucleus of Mrk 6 obtained in 1970–1991
using the image tube spectrograph at the 2.6-m Shajn telescope of
the Crimean Astrophysical Observatory. We analyze 363 spectra for
181 dates obtained in the Hβ spectral region. The spectra in
the Hα region (194 spectra for 179 dates) were used to
get light curves. The light curves in the Hβ and Hα
lines and also in the adjacent continuum show appreciable
variability. Broad-line profile parameters (such as centroid,
width, blue-to-red ratio of fluxes) seem to be independent of or
dependent very weakly on the continuum flux. However, there is a
tendency for the blue-to-red ratio of fluxes to increase with
increasing continuum flux, and also a weak tendency for the
profile width (profile dispersion) to decrease with increasing
continuum flux. An anti-correlation between Hβ shapes at
the blue and red wings, positive correlation between blue shape
and line/continuum flux, and anti-correlation between red shape
and line/continuum flux show that the blue segments respond
slightly better to the continuum changes than the red segment and
total Hβ line. We assume that the observed broad profile
consists of at least two components with fixed profiles. We found
that one of the components is nearly symmetric and has a single
peak, while the other component has a blue bump and extended red
wing. In terms of such a two-broad-components profile model, the
evolution of the observed Hβ profiles can be roughly
reproduced by changes in the relative strength of the two variable
components. However, the evolution of the broad Hβ profile
in Mrk 6 is complicated and not clear at all. The
evolution is driven, most likely, by a set of various factor,
including a multi-component BLR model with redistribution of
ionizing radiation between different parts of the BLR, the matter
redistribution, reverberation effects, and continuum-dependent
changes.

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